Single-Pass Imaging System With Spatial Light Modulator and Catadioptric Anamorphic Optical System

ABSTRACT

A single-pass imaging system utilizes a light source and a spatial light modulator to generate a two-dimensional modulated light field, and uses a catadiotropic anamorphic optical system to anamorphically image and concentrate the modulated light in order to generate a high-intensity, substantially one-dimensional line image on an imaging surface (e.g., the surface of a drum cylinder). The catadiotropic anamorphic optical system utilizes one or more cylindrical/acylindrical lens elements to image the modulated light field in the cross-process direction, and one or more cylindrical/acylindrical mirror elements to image and concentrate the modulated light field in the process direction. The line image is generated with sufficient energy to evaporate fountain solution from the imaging surface. The imaging system simultaneously generates all component pixel images of the line image, thus facilitating a printing apparatus capable of 1200 dpi or greater.

FIELD OF THE INVENTION

This invention relates to imaging systems utilized, for example, in highspeed printers, and in particular to single-pass high speed imagingsystems.

BACKGROUND OF THE INVENTION

Laser imaging systems are extensively used to generate images inapplications such as xerographic printing, mask and masklesslithographic patterning, laser texturing of surfaces, and laser cuttingmachines. Laser printers often use a raster optical scanner (ROS) thatsweeps a laser perpendicular to a process direction by utilizing apolygon or galvo scanner, whereas for cutting applications lasersimaging systems use flatbed x-y vector scanning.

One of the limitations of the laser ROS approach is that there aredesign tradeoffs between image resolution and the lateral extent of theline image. These tradeoffs arising from optical performance limitationsat the extremes of the line image such as image field curvature. Inpractice, it is extremely difficult to achieve 1200 dpi resolutionacross a 20″ imaging swath with single galvanometers or polygonscanners. Furthermore, a single laser head motorized x-y flatbedarchitecture, ideal for large area coverage, is too slow for most highspeed printing processes.

For this reason, monolithic light emitting diode (LED) arrays of up to20″ in width have an imaging advantage for large width xerography.Unfortunately, present LED array are only capable of offering 10milliWatt power levels per pixel and are therefore only useful for somenon-thermal imaging applications such as xerography. In addition, LEDbars have differential aging and performance spread. If a single LEDfails it requires the entire LED bar be replaced. Many other imaging ormarking applications require much higher power. For example, lasertexturing, or cutting applications can require power levels in the10W-100W range. Thus LED bars cannot be used for these high powerapplications. Also, it is difficult to extend LEDs to higher speeds orresolutions above 1200 dpi without using two or more rows of staggeredheads.

Higher power semiconductor laser arrays in the range of 100 mW-100 Wattsdo exist. Most often they exist in a 1D array format such as on a laserdiode bar often about 1 cm in total width. Another type of high powerdirected light source are 2D surface emitting VCSEL arrays. However,neither of these high power laser technologies allow for the laser pitchbetween nearest neighbors to be compatible with 600 dpi or higherimaging resolution. In addition, neither of these technologies allow forthe individual high speed control of each laser. Thus high powerapplications such as high power overhead projection imaging systems,often use a high power source such as a laser in combination with aspatial light modulator such as a DLP™ chip from Texas Instruments orliquid crystal arrays.

Prior art has shown that if imaging systems are arrayed side by side,they can be used to form projected images that overlap wherein theoverlap can form a larger image using software to stitch together theimage patterns into a seamless pattern. This has been shown in manymaskless lithography systems such as those for PC board manufacturing aswell as for display systems. In the past such arrayed imaging systemsfor high resolution applications have been arranged in such a way thatthey must use either two rows of imaging subsystems or use a double passscanning configuration in order to stitch together a continuous highresolution image. This is because of physical hardware constraints onthe dimensions of the optical subsystems. The double imaging rowconfiguration can still be seamlessly stitched together using a conveyorto move the substrate in single direction but such a system requires alarge amount of overhead hardware real estate and precision alignmentbetween each imaging row.

For the maskless lithography application, the time between exposure anddevelopment of photoresist to be imaged is not critical and thereforethe imaging of the photoresist along a single line does not need beexposed at once. However, sometimes the time between exposure anddevelopment is critical. For example, xerographic laser printing isbased on imaging a photoreceptor by erasing charge which naturallydecays over time. Thus the time between exposure and development is nottime invariant. In such situations, it is desirable for the exposuresystem to expose a single line, or a few tightly spaced adjacent linesof high resolution of a surface at once.

In addition to xerographic printing applications, there are othermarking systems where the time between exposure and development arecritical. One example is the laser based variable data lithographicmarking approach originally disclosed by Carley in U.S. Pat. No.3,800,699 entitled, “FOUNTAIN SOLUTION IMAGE APPARATUS FOR ELECTRONICLITHOGRAPHY”. In standard offset lithographic printing, a static imagingplate is created that has hydrophobic imaging and hydrophilicnon-imaging regions. A thin layer of water based dampening solutionselectively wets the plate and forms an oleophobic layer whichselectively rejects oil-based inks. In variable data lithographicmarking disclosed in U.S. Pat. No. 3,800,699, a laser can be used topattern ablate the fountain solution to form variable imaging regions onthe fly. For such a system, a thin layer of dampening solution alsodecays in thickness over time, due to natural partial pressureevaporation into the surrounding air. Thus it is also advantageous toform a single continuous high power laser imaging line pattern formed ina single imaging pass step so that the liquid dampening film thicknessis the same thickness everywhere at the image forming laser ablationstep. However, for most arrayed high power high resolution imagingsystems, the hardware and packaging surrounding a spatial lightmodulator usually prevent a seamless continuous line pattern to beimaged. Furthermore, for many areas of laser imaging such as texturing,lithography, computer to plate making, large area die cutting, orthermal based printing or other novel printing applications, what isneeded is laser based imaging approach with high total optical powerwell above the level of 1 Watt that is scalable across large processwidths in excess of 20″ as well as having achievable resolution greaterthan or equal to 600 dpi, pixel positioning resolution or addressabilitygreater than or equal to 1200 dpi and allows high resolution high speedimaging in a single pass.

SUMMARY OF THE INVENTION

The present invention is directed to an imaging system that utilizes acatadioptric anamorphic optical system to anamorphically image andconcentrate a relatively low intensity two-dimensional modulated lightfield in order to form a substantially one-dimensional high intensityline image that is aligned in a cross-process (e.g., horizontal)direction on an imaging surface. The two-dimensional modulated lightfield is made up of low-intensity light portions that effectively form a“stretched” line image in which each dot-like pixel image portion of theline image is expanded in the process (e.g., vertical) direction.Utilizing the catadioptric anamorphic optical system to image andconcentrate the low-intensity modulated light field in this mannerfacilitates simultaneously generating high total optical intensity(i.e., flux density on the order of hundreds of Watts/cm²) along theentire length of the line image, whereby every dot-like pixel imageportion making up the line image is generated at the same time (i.e., ascompared with a rastering system that only applies high power to onepoint of a line image at any given instant).

In accordance with an aspect of the present invention, the catadioptricanamorphic optical system utilizes one or more cylindrical/acylindricallenses and one or more cylindrical/acylindrical mirrors that areoperably positioned and arranged to image and concentrate thetwo-dimensional modulated light field in the process direction such thatthe one-dimensional line image is projected onto the imaging surface.Utilizing one or more cylindrical/acylindrical mirrors to concentratethe modulated light in the process direction onto the imaging surfaceprovides a lower level of distortion and sagittal field curvature alongthe cross-process direction than that achievable by an all-refractiveanamorphic optical system, thereby better facilitating the imaging of asquare or rectangular two-dimensional modulated light field. In oneembodiment the cylindrical/acylindrical lenses are also utilized toexpand the two-dimensional modulated light field in the cross-processdirection (i.e., such that the line image is wider in the cross-processdirection than the cross-process direction width of the two-dimensionalmodulated light field). By simultaneously expanding the modulated lightfield in the cross-process direction and concentrating the modulatedlight field in the process direction with lower distortion and lowersagittal field curvature along the cross-process direction, the presentinvention provides a reliable yet high power imaging system that can beused, for example, for single-pass high resolution high speed printingapplications.

According to an embodiment of the present invention, the catadioptricanamorphic optical system includes a cross-process optical subsystemincluding at least one cylindrical/acylindrical lens elements and aprocess-direction optical subsystem including at least onecylindrical/acylindrical mirror element. The cross-process opticalsubsystem is disposed between the input two-dimensional light field andthe process-direction optical subsystem, and the one or morecylindrical/acylindrical lens elements serve to image thetwo-dimensional modulated light field in the cross-process direction. Inalternative specific embodiments the process-direction optical subsystemincludes either doublet lens elements or triplet lens elements that arearranged to achieve the desired cross-process imaging. This arrangementfacilitates generating a wide scan line that can be combined (“stitched”or blended together with a region of overlap) with adjacent opticalsystems to produce an assembly having a substantially unlimited lengthscan line. An collimating cross-process directioncylindrical/acylindrical field lens is disposed between thecross-process optical subsystem and the source of the two-dimensionallight field, and is positioned to enable locating an aperture stopbetween the doublet or triplet lens elements, thereby enabling efficientcorrection of aberrations using a low number of simple lenses, and alsoand minimizes the size of doublet/triplet lens elements. The processoptical subsystem is located between the cross-process optical subsystemand the imaging surface (i.e., the optical system output), and includeseither a single process-direction cylindrical/acylindrical mirror ordoublet process-direction cylindrical/acylindrical mirrors that thatserve to image and concentrate the light field in the process direction.

According to an embodiment of the present invention, the imaging systemutilizes a homogenous light generator a spatial light modulator togenerate and project the two-dimensional modulated light field onto thecatadiotropic anamorphic optical system. In accordance with a specificembodiment, the homogenous light generator uses at least one low-powerlight source and a light homogenizer that homogenizes light beamsgenerated by the light source to form a homogeneous light field. Thespatial light modulator including a two-dimensional array ofindividually configurable light modulating elements that are positionedin the homogeneous light field such that each light modulating elementreceives a corresponding low-intensity homogenous light portion, andeither directs (e.g., passes or reflects) its received homogenous lightportion into the catadiotropic anamorphic optical system, or prevents(e.g., blocks or directs away) its received light portion from reachingthe catadiotropic anamorphic optical system. By modulating homogenouslight in this manner prior to being anamorphically projected andconcentrated, the present invention is able to produce a high power lineimage along the entire imaging region simultaneously, as compared with arastering system that only applies high power to one point of the lineimage at any given instant.

In one embodiment, the catadiotropic anamorphic optical system imagesand concentrates the modulated light portions forming thetwo-dimensional light field in the process direction such that theconcentrated light portions forming the line image on the imagingsurface have a light intensity that is at least two times that of theindividual light portions forming the light field. Because therelatively low power homogenous light is spread over the large number ofmodulating elements and only achieves a high intensity at the imagingsurface, the present invention can be produced using low-cost,commercially available spatial light modulating devices, such as digitalmicromirror (DMD) devices, electro-optic diffractive modulator arrays,or arrays of thermo-optic absorber elements. That is, by utilizing ahomogenizer to spread the high energy laser light out over an extendedtwo-dimensional area, the intensity (Watts/cc) of the light over a givenarea (e.g., over the area of each modulating element) is reduced to anacceptable level such that low cost optical glasses and antireflectivecoatings can be utilized to form spatial light modulator with improvedpower handling capabilities. Spreading the light uniformly out alsoeliminates the negatives imaging effects that point defects (e.g.,microscopic dust particles or scratches) have on total lighttransmission losses.

According to an aspect of the present invention, the spatial lightmodulator includes multiple light modulating elements that are arrangedin a two-dimensional array, and a controller for individuallycontrolling the modulating elements such that a light modulatingstructure of each modulating element is adjustable between an “on”(first) modulated state and an “off” (second) modulated state inaccordance with the predetermined line image data. Each light modulatingstructure is disposed to either pass or impede/redirect the associatedportions of the homogenous light according to its modulated state. Whenone of the modulating elements is in the “on” modulated state, themodulating structure directs its associated modulated light portion in acorresponding predetermined direction (e.g., the element passes orreflects the associated light portion toward the catadiotropicanamorphic optical system). Conversely, when the modulating element isin the “off” modulated state, the associated received light portion isprevented from passing to the catadiotropic anamorphic optical system(e.g., the light modulating structure absorbs/blocks the associatedlight portion, or reflects the associated light portion away from thecatadiotropic anamorphic optical system).

According to an embodiment of the present invention, the lightmodulating elements of the spatial light modulator are arranged in rowsand columns, the catadiotropic anamorphic optical system is arranged toconcentrate light portions received from each column onto an associatedpixel image region of the elongated line image. That is, theconcentrated modulated light portions received from all of the lightmodulating elements in a given column (and in the “on” modulated state)are directed by the catadiotropic anamorphic optical system onto thesame corresponding pixel imaging region of the line image so that theresulting imaging “pixel” is the composite light from all lightmodulating elements in the given column that are in the “on” state. Akey aspect of the present invention lies in understanding that the lightportions passed by each light modulating element represent one pixel ofbinary data that is delivered to the scan image by the anamorphicoptical system, so that the brightness of each pixel image making up theline image is controlled by the number of elements in the associatedcolumn that are in the “on” state. Accordingly, by individuallycontrolling the multiple modulating elements disposed in each column,and by concentrating the light passed by each column onto acorresponding imaging region, the present invention provides an imagingsystem having gray-scale capabilities using constant (non-modulated)homogenous light. In addition, if the position of a group of “on” pixelsin each column is adjusted up or down the column, this arrangementfacilitates software electronic compensation of bow (i.e. “smile” of astraight line) and skew.

According to a specific embodiment of the present invention, the spatiallight modulator comprises a DLP™ chip from Texas Instruments, referredto as a Digital Light Processor in the packaged form. The semiconductorchip itself is often referred to as a Digital Micromirror Device or DMD.This DMD includes an two dimensional array of microelectromechanical(MEMs) mirror mechanisms disposed on a substrate, where each MEMs mirrormechanism includes a mirror that is movably supported between first andsecond tilted positions according to associated control signalsgenerated by a controller. The spatial light modulator and theanamorphic optical system are positioned in a folded arrangement suchthat, when each mirror is in the first tilted position, the mirrorreflects its associated received light portion toward the catadiotropicanamorphic optical system, and when the mirror is in the second tiltedposition, the mirror reflects the associated received light portion awayfrom the anamorphic optical system towards a beam dump. An optional heatsink is fixedly positioned relative to the spatial light modulator toreceive light portions from mirrors disposed in the second tiltedposition towards the beam dump. An optional frame is utilized tomaintain each of the components in fixed relative position. An advantageof a reflective DMD-based imaging system is that the folded optical patharrangement facilitates a compact system footprint.

According to another specific embodiment of the present invention,homogeneous light from a light source directed onto a DMD-type spatiallight modulator is directed onto an imaging drum cylinder, where adamping (fountain) solution is coated onto the outer (imaging) surfaceof the drum cylinder, and the concentrated modulated light from thecatadiotropic anamorphic optical system is used to selectively evaporatethe damping solution prior to passing under a ink supply structure. TheDMD-type spatial light modulator is configured such that predeterminedgroups of MEMs mirror mechanisms are activated in accordance with thegray-scale value of an associated image pixel data portion during a(first) time period, and the resulting modulated light is imaged andconcentrated by the anamorphic optical system as described above togenerate a line image by removing fountain solution from an elongatedscanning region of the outer drum surface. When the drum cylindersubsequently rotates such that surface region has passed under inksource, ink material is disposed on exposed surface region to form anink feature. When further rotation causes the ink feature to pass atransfer point, the adhesion between the ink material and the surfaceregion causes transfer of the ink feature to a print medium, resultingin a “dot” in the ink printed on the print medium. Further rotation thedrum cylinder moves the surface region under cleaning mechanism thatremoves any residual ink and fountain solution material to prepare thesurface region for a subsequent exposure/print cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings, where:

FIG. 1 is a top side perspective view showing a simplified imagingsystem utilizing a catadiotropic anamorphic optical system in accordancewith an exemplary embodiment of the present invention;

FIG. 2 is a partial top side perspective view showing a portion of theimaging system of FIG. 1 in additional detail;

FIG. 3 is a simplified side view showing the imaging system of FIG. 1during an imaging operation according to an embodiment of the presentinvention;

FIGS. 4(A) and 4(B) are simplified top and side views, respectively,showing a catadiotropic anamorphic optical system utilized by imagingsystem of FIG. 1 according to a specific embodiment of the presentinvention;

FIG. 5 is a perspective view showing a portion of a DMD-type spatiallight modulator utilized by imaging system of FIG. 1 according to aspecific embodiment of the present invention;

FIG. 6 is an exploded perspective view showing a light modulatingelement of the DMD-type spatial light modulator of FIG. 5 in additionaldetail;

FIGS. 7(A), 7(B) and 7(C) are perspective views showing the lightmodulating element of FIG. 6 during operation;

FIG. 8 is a perspective view showing an imaging system utilizing aDMD-type spatial light modulator and a catadiotropic anamorphic opticalsystem in a folded arrangement according to another specific embodimentof the present invention;

FIG. 9 is a simplified side view showing the imaging system of FIG. 8during an imaging operation;

FIGS. 10(A), 10(B) and 10(C) are simplified side views showing theimaging system of FIG. 9 during an image transfer operation;

FIG. 11 is a simplified top view showing a imaging system including acatadioptric anamorphic optical system according to another specificembodiment of the present invention;

FIG. 12 is a simplified side view showing the imaging system of FIG. 11during operation;

FIG. 13 is a simplified top view showing another imaging systemincluding a catadioptric anamorphic optical system according to anotherspecific embodiment of the present invention; and

FIG. 14 is a simplified side view showing the imaging system of FIG. 13during operation;

FIG. 15 is a perspective view showing an imaging system utilizing aDMD-type spatial light modulator and a multi-mirror catadiotropicanamorphic optical system in a folded arrangement according to anotherspecific embodiment of the present invention;

FIG. 16 is a simplified top view showing a imaging system including amulti-mirror catadioptric anamorphic optical system according to anotherspecific embodiment of the present invention;

FIG. 17 is a simplified side view showing the imaging system of FIG. 16during operation;

FIG. 18 is a simplified top view showing another imaging systemincluding a multi-mirror catadioptric anamorphic optical systemaccording to another specific embodiment of the present invention; and

FIG. 19 is a simplified side view showing the imaging system of FIG. 18during operation.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention relates to improvements in imaging systems andrelated apparatus (e.g., scanners and printers). The followingdescription is presented to enable one of ordinary skill in the art tomake and use the invention as provided in the context of a particularapplication and its requirements. As used herein, directional terms suchas “upper”, “uppermost”, “lower”, “vertical” and “horizontal” areintended to provide relative positions for purposes of description, andare not intended to designate an absolute frame of reference. As usedherein, reference to the position of optical elements (lenses, mirrors)as being located “between” other optical elements is intended to mean inthe sense of the normal light path through the associated optical systemunless specified otherwise (e.g., a lens is “between” two mirrors when,during normal operation of an optical system including the lens andmirrors, light is reflected from one mirror through the lens to theother mirror). As used herein, the compound term“cylindrical/acylindrical” is intended to mean that an associatedoptical element is either cylindrical (i.e., a cylindrical lens ormirror whose curved optical surface or surfaces are sections of acylinder and focus an image onto a line parallel to the intersection ofthe optical surface and a plane tangent to it), or acylindrical (i.e.,an elongated curved lens or mirror whose curved optical surface orsurfaces are not cylindrical, but still focus an image onto a lineparallel to the intersection of the optical surface and a plane tangentto it). Various modifications to the preferred embodiment will beapparent to those with skill in the art, and the general principlesdefined herein may be applied to other embodiments. Therefore, thepresent invention is not intended to be limited to the particularembodiments shown and described, but is to be accorded the widest scopeconsistent with the principles and novel features herein disclosed.

FIG. 1 is a perspective view showing a simplified single-pass imagingsystem 100 utilized to generate a two-dimensional modulated light field119B in response to image data ID, and to image and concentratetwo-dimensional modulated light field 119B in order to generate asubstantially one-dimensional line image SL on an imaging surface 162(e.g. the surface of a drum cylinder 160). As indicated by the dashedline optical path shown in FIG. 1, single-pass imaging system 100utilizes a homogenous light generator 110 to generate a two-dimensionalhomogeneous light field 119A that is projected onto a spatial lightmodulator 120. Single-pass imaging system 100 utilizes spatial lightmodulator 120, which is controlled as described below by a controller180, to modulate two-dimensional homogeneous light field 119A accordingto one line of image data ID, and to transmit (project) atwo-dimensional modulated light field 119B onto a catadiotropicanamorphic optical system 130. Single-pass imaging system 100 usescatadiotropic anamorphic optical system 130 to image and concentratemodulated light field 119B such that substantially one-dimensional lineimage SL is generated on (project onto) imaging surface 162 utilizingthe optical subsystems and elements described below.

FIGS. 2 and 3 are simplified perspective and side views, respectively,showing portions of imaging system 100 including homogeneous lightsource 110 and spatial light modulator 120, which are utilized togenerate modulated light field 119B, during the generation of a lineimage SL. Note that FIGS. 2 and 3 illustrate the associated optical pathin a “folded out” (linear) form (i.e., where catadioptic anamorphicoptical system 130 is represented as a simplified “pass through” systemby a box) for purposes of describing the generation and subsequentprocessing of modulated light field 119B.

The present invention is herein with reference to exemplary imagingprocesses involving the conversion of digital image data (referred toherein as “image data file ID”) to a corresponding two-dimensional image(e.g., a picture or print document) consisting of a light pattern thatis specified by the digital image data. In particular, the invention isdescribed with reference to an “imaging phase” (portion) of the imagingoperation involving the generation of a single line (referred to forconvenience herein as a “line image”) of the two-dimensional image inaccordance with associated line data (referred to for convenience hereinas a “line image data portion”). As indicted in FIG. 2, exemplaryimaging processes involving the conversion of digital image data to acorresponding two-dimensional image consisting of a light pattern thatis specified by the digital image data and in particular to thegeneration of a of the that is stored according to known techniques and.In such imaging image data file ID is depicted at the bottom of FIG. 2being transmitted to controller 180, which processes image data file IDin the manner described below, and transmits image data file ID one lineat a time to spatial light modulator 120. That is, consistent with moststandardized image file formats, image data file ID is made up ofmultiple line image data groups LID1 to LIDn, where each line image datagroup includes multiple pixel image data portions that collectively forman associated one-dimensional line image of the two-dimensional image.For example, in the simplified example shown in FIG. 2, line image datagroup LID1 includes four pixel image data portions PID1 to PID3. Eachpixel image data portion (e.g., pixel image data portion PID1) includesone or more bits of image data corresponding to the color and/orgray-scale properties of the corresponding pixel image associated withthe corresponding portion of the two-dimensional image. Those skilled inthe art will recognize that, in practical embodiments, each line imagedata group typically includes a much larger number of pixel image dataportions that the four-, eight-, or twenty-four pixel image rowsdescribed herein.

Referring to the lower left portion of FIG. 2 and to FIG. 3, homogenouslight generator 110 generates homogenous light field 119A usingcontinuous (i.e., constant/non-modulated) homogenous light 118A having aconstant energy level (i.e., such that all portions of homogenous lightfield 119A have substantially the same flux density). In an exemplaryspecific embodiment shown in FIG. 3, homogeneous light generator 110comprises a light source 112 including a light generating element (e.g.,one or more lasers or light emitting diodes) 115 fabricated or otherwisedisposed on a suitable carrier (e.g., a semiconductor substrate) 111,and a light homogenizing optical system (homogenizer) 117 that isdisposed between light source 112 and spatial light modulator 120.Homogenizer 117 generates homogenous light 118 by homogenizing (i.e.,mixing and spreading out) light beam 116 over an extendedtwo-dimensional area, and reduces any divergences of light beams 116.Those skilled in the art will recognize that this arrangementeffectively converts the concentrated, relatively high energy intensityand high divergence of light beam 116 into dispersed, relatively lowenergy flux homogenous light 118 that is substantially evenlydistributed onto all modulating elements (e.g., modulating elements125-11 to and 125-34) of spatial light modulator 120. In an exemplaryembodiments, homogeneous light source 110 is implemented by multipleedge emitting laser diodes arranged along a straight line that isdisposed parallel to the rows of light modulating elements (not shown),or multiple vertical cavity surface emitting lasers (VCSELs) arearranged in a two-dimensional array. Ideally such laser sources wouldhave high plug efficiencies (e.g., greater than 50%) so that passivewater cooling or forced air flow could be used to easily take awayexcess heat. Light homogenizer 117 can be implemented using any ofseveral different technologies and methods known in the art includingbut not limited to the use of a fast axis concentrator (FAC) lenstogether with microlens arrays for beam reshaping, or additionally alight pipe approach which causes light mixing within a waveguide.

Referring back to the left center left portion of FIG. 2, spatial lightmodulator 120 is disposed in homogenous light field 119A, and includes amodulating element array 122 and a control circuit 126. Spatial lightmodulator 120 serves the purpose of modulating portions of homogenouslight 118A in accordance with the method described below, wherebyspatial light modulator 120 converts homogenous light field 119A into atwo-dimensional modulated light field 119B that is projected throughcatadioptric anamorphic optical system 130 onto an elongated imagingregion 167 of imaging surface 162. In a practical embodiment such aspatial light modulator can be purchased commercially and wouldtypically have two-dimensional (2D) array sizes of 1024×768 (SVGAresolution) or higher resolution with light modulation element (pixel)spacing on the order of 5-20 microns. For purposes of illustration, onlya small subset of light modulation elements is depicted in FIG. 2.

Referring to the left-center region of FIG. 2, modulating element array122 of spatial light modulator 120 includes modulating elements 125-11to 125-34 that are disposed in four horizontal rows and three verticalcolumns C1-C3 on a support structure 124. Modulating elements 125-11 to125-34 are disposed in homogenous light field 119A such that a lightmodulating structure (e.g., a mirror, a diffractive element, or athermo-optic absorber element) of each modulating element receives acorresponding portion of homogenous light 118A (e.g., modulatingelements 125-11 and 125-12 respectively receive homogenous lightportions 118A-11 and 118A-12), and is positioned to selectively pass orredirect the received corresponding modulated light portion along apredetermined direction toward catadioptric anamorphic optical system130 (e.g., modulating element 125-11 allows received light portion118A-11 to pass to catadioptric anamorphic optical system 130, butmodulating element 125-21 blocks/redirects/prevents received lightportion 118A-21 from passing to catadioptric anamorphic optical system130).

Referring to the lower right region of FIG. 2, control circuit 126includes an array of control (memory) cells 128-11 to 128-34 that storeone line image data portion (e.g., line image data portion LIN1) duringeach imaging phase of an imaging operation. For example, at a giventime, line image data portion LIN1 is transmitted (written) fromcontroller 180 to control circuit 126 using known techniques, and lineimage data portion LIN1 is used to generate a corresponding line imageSL in an elongated imaging region 167 of imaging surface 162. During asubsequent imaging phase (not shown), a second line image data portionis written into control circuit 126 (i.e., line image data portion LIN1is overwritten), and a corresponding second line image (not shown) isgenerated in another elongated imaging region of imaging surface 162.Note that this process requires movement (translation) of imagingsurface 162 in the process (Y-axis) direction after line image SL isgenerated and before the second line image is generated. Those skilledin the art will recognize that, by repeating such imaging phases foreach scan image data portion LIN1-LINn of image data file ID, theassociated two-dimensional image is generated on imaging surface 162.

In the exemplary embodiment shown in FIG. 2, each memory cell 128-11 to128-34 of control circuit 126 stores a single data bit (1 or 0), andeach light modulating element 125-11 to 125-34 is respectivelyindividually controllable by way of the data bit stored in an associatedmemory cell 128-11 to 128-34 (e.g., by way of control signals 127) toswitch between an “on” (first) modulated state and an “off” (second)modulated state. When the associated memory cell of a given modulatingelement stores a logic “1” value, the given modulating element iscontrolled to enter an “on” modulated state, whereby the modulatingelement is actuated to direct the given modulating element's associatedreceived light portion toward anamorphic optic 130. For example, in thesimplified example, modulating element 125-11 is turned “on” (e.g.,rendered transparent) in response to the logic “1” stored in memory cell128-11, whereby received light portion 118A-11 is passed through spatiallight modulator 120 and is directed toward anamorphic optic 130.Conversely, modulating element 125-21 is turned “off” (e.g., renderedopaque) in response to the logic “0” stored in memory cell 128-21,whereby received light portion 118A-21 is blocked (prevented frompassing to anamorphic optic 130). By selectively turning “on” or “off”modulating elements 125-11 to 125-34 in accordance with image data ID inthe manner described herein, spatial light modulator 120 serves tomodulate (i.e., pass or not pass) portions of continuous homogenouslight 118A such that the modulated light is directed onto catadioptricanamorphic optical system 130. As set forth in additional detail below,spatial light modulator 120 is implemented using any of severaltechnologies, and is therefore not limited to the linear “pass through”arrangement depicted in FIGS. 1 to 3.

As used herein, the portions of homogenous light 118A (e.g., homogenouslight portion 118A-24) that are passed through or otherwise directedfrom spatial light modulator 120 toward anamorphic optic 130 areindividually referred to as modulated light portions, and collectivelyreferred to as modulated light 118B or two-dimensional modulated lightfield 119B. For example, after passing through light modulating element125-11, which is turned “on”, homogenous light portion 118A-21 becomesmodulated light portion 118B-11, which is passed to anamorphic opticsystem 130 along with light portions passed through light modulatingelements 125-12, 125-13, 125-14, 125-32 and 125-33, as indicated by thelight colored areas of the diagram depicting modulated light field 119B.Conversely, when a given modulating element (e.g., modulating element125-21) is in the “off” modulated state, the modulating element isactuated to prevent (e.g., block or redirect) the given modulatingelement's associated received light portion, whereby the correspondingregion of the diagram depicting modulated light field 119B is dark.

Referring to FIG. 1, catadioptric anamorphic optical system 130 servesto anamorphically image and concentrate (focus) two-dimensionalmodulated light field 119B onto elongated imaging region 167 of imagingsurface 162. In particular, catadioptric anamorphic optical system 130includes a cross-process optical subsystem 133 for imagingtwo-dimensional modulated light field 119B in the cross-process (X-axis)direction, and a process-direction optical subsystem 137 for imaging andconcentrating two-dimensional modulated light field 119B in the process(Y-axis) direction. For illustrative purposes, cross-process opticalsubsystem 133 and process-direction optical subsystem 137 areillustrated in the simplified embodiment shown in FIG. 1 by acylindrical/acylindrical lens element 134 and cylindrical/acylindricalmirror element 138, respectively, although each subsystem typicallyincludes two or more optical elements, as set forth below with referenceto the specific embodiments. Cylindrical/acylindrical lens element 134is positioned to receive two-dimensional modulated light field 119B fromspatial light modulator 120, and is shaped and arranged to imagetwo-dimensional modulated light field 119B in the cross-process (X-axis)direction. The processed light passed from cross-process opticalsubsystem 133 to process-direction optical subsystem 137, which isindicated by dot-dot-dash lines in FIG. 1, is referred to herein asimaged light 119C1. In accordance with an aspect of the invention,cross-process optical subsystem 133 images the modulated light such thata width W2 of line image SL in the cross-process (X-axis) direction isequal to or greater than an original width W1 of two-dimensionalmodulated light field 119B. Cylindrical/acylindrical mirror element 138is positioned to receive imaged light 119C1 from cross-process opticalsubsystem 133, and is shaped and arranged to image and concentrateimaged light 119C1 in the process (e.g., Y-axis) direction. The imagedand concentrated light passed from process-direction optical subsystem137 to imaging surface 162, which is indicated by dot-dash-dash line inFIG. 1, is referred to herein as imaged and concentrated light 119C2.Note that modulated light field 119B is concentrated by optical system130 to a greater degree along the process (e.g., Y-axis) direction thanalong the cross-process (X-axis) direction, whereby the receivedmodulated light portions are anamorphically focused to formsubstantially one-dimensional line image SL that extends in the process(X-axis) direction on imaging surface 162, as indicated in FIG. 1. Thatis, process-direction optical subsystem 137 images the modulated lightsuch that a height H2 of line image SL in the process (Y-axis) directionis substantially (e.g., three or more times) smaller than an originalheight H1 of two-dimensional modulated light field 119B. Due to processdirection distortion, catadioptric anamorphic projection optical systemare more suitable for imaging systems where the two-dimensional lightfield 119B is much wider in the cross-process direction that in theprocess direction. By utilizing at least one cylindrical/acylindricalmirror element 138, catadiotropic anamorphic optical system 130 exhibitsa lower level of distortion in the process direction and lower sagittalfield curvature across the cross-process direction than that possiblewith an all-refractive anamorphic optical system, thereby facilitatingsuperior imaging of square or rectangular two-dimensional modulatedlight field 119B.

FIGS. 4(A) and 4(B) are top view and side view diagrams showing aportion of an imaging system 100E including a spatial light modulator120E and a simplified catadioptric anamorphic optical system 130Eaccording to an alternative embodiment of the present invention. Spatiallight modulator 120E operates in the manner described above to project atwo-dimensional modulated light field 119B onto catadioptric anamorphicoptical system 130E. According to the present exemplary embodiment,catadioptric anamorphic optical system 130E generally includes acollimating optical subsystem 131E, a cross-process optical subsystem133E, and process-direction optical subsystem 137E. As indicated by thedash/dot ray trace lines in FIGS. 4(A) and 4(B), optical subsystems131E, 133E and 137E are disposed in the optical path between spatiallight modulator 120E and imaging surface 162E, which is located at theoutput end of imaging system 100E.

FIG. 4(A) is a top view indicating that collimating optical subsystem131E and cross-process optical subsystem 133E image modulated lightfield 119B in the cross-process (X-axis) direction. Collimating opticalsubsystem 131E includes a cylindrical/acylindrical collimating fieldlens 132E formed in accordance with known techniques that is locatedimmediately after spatial light modulator 120E, and arranged tocollimate the light portions that are slightly diverging off of thesurface of the spatial light modulator 120E. Collimating opticalsubsystem 131E is optional, and may be omitted when modulated lightportions 118B leaving spatial light modulator 120 are already wellcollimated. Cross-process optical subsystem 133E is positioned toreceive modulated light field 119B from spatial light modulator 120E,and includes a cylindrical/acylindrical lens 134E shaped and arranged toimage modulated light field 119B in the cross-process X-axis direction.FIG. 4(A) also indicates that, in one embodiment, cross-process opticalsubsystem 133E acts to expand modulated light field 119B in thecross-process direction.

FIG. 4(B) is a side view that indicates how process-direction opticalsubsystem 137E acts on modulated light portions 118B passed by spatiallight modulator 120E and generate imaged and concentrated light field119C1 that forms scan line SL on imaging surface 162E. Process-directionoptical subsystem 137E includes a cylindrical/acylindrical mirror 138Ethat is shaped and arranged to image and concentrate imaged modulatedlight 119C1 received from cross-process optical subsystem 133E in theprocess (Y-axis) direction, whereby imaged and concentrated modulatedlight 119C2 is directed onto imaging surface 162E to generatesubstantially one-dimensional line image SL in the manner describedabove. The advantage of positioning process-direction optical subsystem137E after cross-process optical subsystem 133E in the optical path isthat it allows the intensity of the light (e.g., laser) power to beconcentrated on scan line SL located at the output of single-passimaging system 100E. As the focusing power of cylindrical/acylindricalmirror 138E is increased, the intensity of the light on spatial lightmodulator 120E is reduced relative to the intensity of the line imagegenerated at line image SL. However, this means thatcylindrical/acylindrical mirror 138E must be placed closer to imagingsurface 162E (e.g., the surface of an imaging drum cylinder) with aclear aperture extending to the very edges of mirror 138E.

Referring again to FIG. 2, by utilizing catadioptric anamorphic opticalsystem 130 to concentrate modulated light field 119B in the process(Y-axis) direction, a “single-pass” substantially one-dimensional lineimage SL is formed on imaging surface 162 that extends in thecross-process (X-axis) direction. When a given pixel image (e.g.,portion P1) is generated by activating all modulating elements (e.g.,125-11 to 125-14) of a given group (e.g., group G1), high total opticalintensity (flux density, e.g., on the order of hundreds of Watts/cm²) isgenerated on a given point of line image SL, thereby facilitating areliable, high speed imaging system that can be used, for example, tosimultaneously produce all portions of a one-dimensional line image SLin a single-pass high resolution high speed printing application.

In accordance with an aspect of the present invention, multi-level imageexposure at lower optical resolution is utilized to achieve high qualityimaging (e.g., in a printer) by varying the exposure level (i.e., theamount of concentrated light) directed onto each pixel image location ofline image SL. In particular, the exposure level for each pixel image(e.g., portions P1, P2 and P3 in FIG. 1) in line image SL is varied bycontrolling the number and location of the activated light modulatingelements of spatial light modulator 120, thereby controlling the amountand location of modulated light 118B that is combined to generate eachpixel image. This approach provides a significant improvement overconventional laser ROS operations in that, instead of modulating a highpower laser while scanning the laser beam using high optical resolutionacross an imaging surface to provide multi-level (gray-scale) imageexposure properties, the present invention simultaneously providesmulti-level image exposure at all locations of line image SL bymodulating a relatively low power light source and by utilizing arelatively low optical resolution imaging system to focus the modulatedlight onto imaging surface 162. That is, by utilizing a homogeneouslight that is spread out over an extended two-dimensional area, theintensity (Watts/cm²) of the light over a given area (e.g., over thearea of each modulating element 125-11 to 125-34) is reduced to anacceptable level such that low cost optical glasses and antireflectivecoatings can be utilized to form spatial light modulator 120, thusreducing manufacturing costs. Uniformly spreading the light alsoeliminates the negative imaging effects that point defects (e.g.,microscopic dust particles or scratches) have on total lighttransmission losses.

Multi-level image exposure is achieved by imaging system 100 by forminggroups of light modulating elements that are substantially aligned inthe process (Y-axis) direction defined by the catadioptric anamorphicoptical system, configuring each modulating element group in accordancewith an associated pixel image data portion of the line image data groupwritten into the spatial light modulator, and then utilizingcatadioptric anamorphic optical system 130 to image and concentrate theresulting elongated pixel image in the process direction to form ahigh-intensity pixel image portion of image line SL. For example, in theexemplary embodiment shown in FIG. 1, spatial light modulator 120 isarranged relative to catadioptric anamorphic optical system 130 suchthat modulating element columns C1 to C3 are aligned parallel to theprocess (Y-axis) direction defined by catadioptric anamorphic opticalsystem 130. In this arrangement, each modulating element group consistsof the modulating elements disposed in each of the columns C1 to C3,where group G1 includes all modulating elements (i.e., elements 125-11to 125-14) of column C1, group G2 includes modulating elements 125-21 to125-24) of column C2, and group G3 includes modulating elements 125-31to 125-34) of column C3. The images generated by each group/columneffectively form pixel images that are “stretched” (elongated) in theprocess (Y-axis) direction (e.g., light elements 118B-11 to 118B-14 forma first elongated “bright” pixel image associated with pixel dataPID11). Because catadioptric anamorphic optical system 130 generateseach pixel image (e.g., pixel image P1) of line image SL byconcentrating modulated light portions in the process direction, thegray-scale properties of each pixel image P1 can be controlled byconfiguring a corresponding number of modulating elements (e.g.,elements 125-11 to 125-14) that are aligned in the process (Y-axis)direction. By utilizing controller 180 to interpret the gray-scale valueof each pixel image data portion (e.g., pixel image data portion PID1)and to write corresponding control data into control cells (e.g., cells128-11 to 128-14) of the modulating element group (e.g., group G1)associated with that pixel image data portion, the appropriate pixelimage is generated at each pixel location of line image SL.

FIG. 2 shows multi-level image exposure using three exposure levels:“fully on”, “fully off” and “partially on”. In the simplified exampleshown in FIGS. 1 and 2, pixel image data portion PID1 has a “fully on”(first) gray-scale value, whereby controller 180 writes pixel image dataportion PID1 to control circuit 126 of spatial light modulator 120 suchthat all modulating elements 125-11 to 125-14 of associated modulatingelement group G1 are activated (i.e., configured into the “on” (first)modulated state). Because modulating elements 125-11 to 125-14 areactivated, homogeneous light portions 118A-11 to 118A-14 of homogeneouslight field 119A are passed through modulating elements 125-11 to 125-14such that modulated light portions 118B-11 to 118B-14 of modulated lightfield 119B are directed onto the catadioptric anamorphic optical system130. Similarly, pixel image data portion PID2 has a “fully off” (second)value, so all of modulating elements 125-21 to 125-24 of associatedmodulating element group G2 are deactivated (i.e., configured into an“off” (second) modulated state) such that homogeneous light 118A (e.g.,homogeneous light portion 118A-21) that is directed onto modulatingelements 125-21 to 125-24 are prevented (i.e., blocked or redirected)from reaching catadioptric anamorphic optical system 130, therebygenerating light pixel image P2 as a minimum (dark) image “spot” in asecond imaging region portion 167-2 on imaging surface 162. Finally, thegray-scale value of pixel image data portion PID3 is “partially on”,which is achieved by configuring light modulating elements 125-31 to125-34 such that modulating elements 125-32 and 125-33 are activated andmodulating elements 125-31 and 125-34 are deactivated, causinghomogeneous light portions to pass only through modulating elements125-32 to 125-33 to catadioptric anamorphic optical system 130, wherebypixel image P3 is formed in third imaging region portion 167-3 ofimaging surface 162 as a small bright “spot”.

Those skilled in the art will understand that the production of atwo-dimensional image using the system and method described aboverequires periodic or continuous movement (i.e., scrolling) of imagingsurface 162 in the process (Y-axis) direction and reconfiguring spatiallight modulator 120 after each imaging phase. For example, aftergenerating line image SL using line image data group LIN1 as shown inFIG. 1, imaging surface 162 is moved upward and a second imaging phaseis performed by writing a next sequential line image data group intospatial light modulator 120, whereby a second line image is generated asdescribed above that is parallel to and positioned below line image SL.Note that light source 110 is optionally toggled between imaging phases,or maintained in an “on” state continuously throughout all imagingphases of the imaging operation. By repeating this process for all lineimage data groups LIN1-LINn of image data file ID, the two-dimensionalimage represented by image data file ID is generated on imaging surface162.

According to alternative embodiments of the present invention, thespatial light modulator is implemented using commercially availabledevices including a digital micromirror device (DMD), such as a digitallight processing (DLP®) chip available from Texas Instruments of DallasTex., USA, an electro-optic diffractive modulator array such as theLinear Array Liquid Crystal Modulator available from Boulder NonlinearSystems of Lafayette, Colo., USA, or an array of thermo-optic absorberelements such as Vanadium dioxide reflective or absorbing mirrorelements. Other spatial light modulator technologies may also be used.While any of a variety of spatial light modulators may be suitable for aparticular application, many print/scanning applications today require aresolution 1200 dpi and above, with high image contrast ratios over10:1, small pixel size, and high speed line addressing over 30 kHz.Based on these specifications, the currently preferred spatial lightmodulator is the DLP™ chip due to its best overall performance.

FIG. 5 is a perspective view showing a portion of a DMD-type spatiallight modulator 120G including a modulating element array 122G made upof multiple microelectromechanical (MEMs) mirror mechanisms 125G.DMD-type spatial light modulator 120G is utilized in accordance with aspecific embodiment of the present invention. Modulating element array122G is consistent with DMDs sold by Texas Instruments, wherein MEMsmirror mechanisms 125G are arranged in a rectangular array on asemiconductor substrate (i.e., “chip” or support structure) 124G. Mirrormechanism 125G are controlled as described below by a control circuit126G that also is fabricated on substrate 124G according to knownsemiconductor processing techniques, and is disposed below mirrors 125G.Although only sixty-four mirror mechanisms 125G are shown in FIG. 5 forillustrative purposes, those skilled in the art will understand that anynumber of mirror mechanisms are disposed on DMD-type modulating elementarray 122G, and that DMDs sold by Texas Instruments typically includeseveral hundred thousand mirrors per device.

FIG. 6 is a combination exploded perspective view and simplified blockdiagram showing an exemplary mirror mechanism 125G-11 of DMD-typemodulating element array 122G (see FIG. 5) in additional detail. Fordescriptive purposes, mirror mechanism 125G-11 is segmented into anuppermost layer 210, a central region 220, and a lower region 230, allof which being disposed on a passivation layer (not shown) formed on anupper surface of substrate 124G. Uppermost layer 210 of mirror mechanism125G-11 includes a square or rectangular mirror (light modulatingstructure) 212 that is made out of aluminum and is typicallyapproximately 16 micrometers across. Central region 220 includes a yoke222 that connected by two compliant torsion hinges 224 to support plates225, and a pair of raised electrodes 227 and 228. Lower region 230includes first and second electrode plates 231 and 232, and a bias plate235. In addition, mirror mechanism 125G-11 is controlled by anassociated SRAM memory cell 240 (i.e., a bi-stable flip-flop) that isdisposed on substrate 124G and controlled to store either of two datastates by way of control signal 127G-1, which is generated by controlcircuit 126G in accordance with image data as described in additionaldetail below. Memory cell 240 generates complementary output signals Dand D-bar that are generated from the current stored state according toknown techniques.

Lower region 230 is formed by etching a plating layer or otherwiseforming metal pads on a passivation layer (not shown) formed on an uppersurface of substrate 124G over memory cell 240. Note that electrodeplates 231 and 232 are respectively connected to receive either a biascontrol signal 127G-2 (which is selectively transmitted from controlcircuit 126G in accordance with the operating scheme set forth below) orcomplementary data signals D and D-bar stored by memory cell 240 by wayof metal vias or other conductive structures that extend through thepassivation layer.

Central region 220 is disposed over lower region 230 using MEMStechnology, where yoke 222 is movably (pivotably) connected andsupported by support plates 225 by way of compliant torsion hinges 224,which twist as described below to facilitate tilting of yoke 222relative to substrate 124G. Support plates 225 are disposed above andelectrically connected to bias plate 235 by way of support posts 226(one shown) that are fixedly connected onto regions 236 of bias plate235. Electrode plates 227 and 228 are similarly disposed above andelectrically connected to electrode plates 231 and 232, respectively, byway of support posts 229 (one shown) that are fixedly connected ontoregions 233 of electrode plates 231 and 232. Finally, mirror 212 isfixedly connected to yoke 222 by a mirror post 214 that is attached ontoa central region 223 of yoke 222.

FIGS. 7(A) to 7(C) are perspective/block views showing mirror mechanism125G-11 of FIG. 5 during operation. FIG. 7(A) shows mirror mechanism125G-11 in a first (e.g., “on”) modulating state in which received lightportion 118A-G becomes reflected (modulated) light portion 118B-G1 thatleaves mirror 212 at a first angle θ1. To set the “on” modulating state,SRAM memory cell 240 stores a previously written data value such thatoutput signal D includes a high voltage (VDD) that is transmitted toelectrode plate 231 and raised electrode 227, and output signal D-barincludes a low voltage (ground) that is transmitted to electrode plate232 and raised electrode 228. These electrodes control the position ofthe mirror by electrostatic attraction. The electrode pair formed byelectrode plates 231 and 232 is positioned to act on yoke 222, and theelectrode pair formed by raised electrodes 227 and 228 is positioned toact on mirror 212. The majority of the time, equal bias charges areapplied to both sides of yoke 222 simultaneously (e.g., as indicated inFIG. 7(A), bias control signal 127G-2 is applied to both electrodeplates 227 and 228 and raised electrodes 231 and 232). Instead offlipping to a central position, as one might expect, this equal biasactually holds mirror 122 in its current “on” position because theattraction force between mirror 122 and raised electrode 231/electrodeplate 227 is greater (i.e., because that side is closer to theelectrodes) than the attraction force between mirror 122 and raisedelectrode 232/electrode plate 228.

To move mirror 212 from the “on” position to the “off” position, therequired image data bit is loaded into SRAM memory cell 240 by way ofcontrol signal 127G-1 (see the lower portion of FIG. 7(A). As indicatedin FIG. 7(A), once all the SRAM cells of array 122G have been loadedwith image data, the bias control signal is de-asserted, therebytransmitting the D signal from SRAM cell 240 to electrode plate 231 andraised electrode 227, and the D-bar from SRAM cell 240 to electrodeplate 232 and raised electrode 228, thereby causing mirror 212 to moveinto the “off” position shown in FIG. 7(B), whereby received lightportion 118A-G becomes reflected light portion 118B-G2 that leavesmirror 212 at a second angle θ2. In one embodiment, the flat uppersurface of mirror 212 tilts (angularly moves) in the range ofapproximately 10 to 12° between the “on” state illustrated in FIG. 7(A)and the “off” state illustrated in FIG. 7(B). When bias control signal127G-2 is subsequently restored, as indicated in FIG. 7(C), mirror 212is maintained in the “off” position, and the next required movement canbe loaded into memory cell 240. This bias system is used because itreduces the voltage levels required to address the mirrors such thatthey can be driven directly from the SRAM cells, and also because thebias voltage can be removed at the same time for the whole chip, soevery mirror moves at the same instant.

As indicated in FIGS. 7(A) to 7(C), the rotation torsional axis ofmirror mechanism 125G-11 causes mirrors 212 to rotate about a diagonalaxis relative to the x-y coordinates of the DLP chip housing. Thisdiagonal tilting requires that the incident light portions received fromthe spatial light modulator in an imaging system be projected onto eachmirror mechanism 125G at a compound incident angle so that the exitangle of the light is perpendicular to the surface of the DLP chip. Thisrequirement complicates the side by side placement of imaging systems.

FIG. 8 is a perspective view showing an imaging system 100H utilizing aDMD-type spatial light modulator 120H that are positioned in a “folded”arrangement, and includes a simplified catadioptric anamorphic opticalsystem 130H according to a specific embodiment of the present invention.Spatial light modulator 120H is essentially identical to DMD-typespatial light modulator 120G (described above), and is positioned at acompound angle relative to homogenous light generator 110H andcatadioptric anamorphic optical system 130H such that incidenthomogenous light portion 118A of homogenous light field 119A are eitherreflected toward catadioptric anamorphic optical system 130H whenassociated MEMs mirror mechanisms 125H of spatial light modulator 120Hare in the “on” position, or reflected away from catadioptric anamorphicoptical system 130H (e.g., onto a heat sink, not shown) when associatedMEMs mirror mechanisms 125H of spatial light modulator 120H are in the“off” position. That is, each light portions 118A of homogenous lightfield 119A that is directed onto an associated MEMs mirror mechanism125H of spatial light modulator 120H from homogenous light generator110H is reflected from the associated MEMs mirror mechanism 125H tocatadioptric anamorphic optical system 130 only when the associated MEMsmirror mechanism 125H is in the “on” position (e.g., as described abovewith reference to FIG. 7(A)). Conversely, each MEMs mirror mechanism125H that is in the “off” position reflects an associated light portion118B at angle that directs the associated light portion 118B away fromcatadioptric anamorphic optical system 130H. In one embodiment, thecomponents of imaging system 100H are maintained in the “folded”arrangement by way of a rigid frame that is described in detail inco-owned and co-pending application Ser. No. ______ [Atty Ref. No.20090938-US-NP (XCP-146-1)], entitled SINGLE-PASS IMAGING SYSTEM USINGSPATIAL LIGHT MODULATOR AND ANAMORPHIC PROJECTION OPTICS, which isincorporated herein by reference in its entirety.

DMD-type imaging system 100H is characterized in that catadioptricanamorphic optical system 130H inverts modulated light field 119B inboth the process and cross-process directions such that the position andleft-to-right order of the two line images generated on drum cylinder160H are effectively “flipped” in both the process and cross-processdirections. The diagram at the lower left portion of FIG. 8 shows afront view of DMD-type spatial light modulator 120H, and the diagram atthe lower right portion of FIG. 8 shows a front view of elongatedimaging region 167H of imaging surface 162H. Similar to the embodimentdescribed above with reference to FIG. 1, the lower left diagram showsthat modulating element column C1 forms a first modulating element groupG1 that is controlled by a first pixel image data portion PID11 of lineimage data portions LIN11. Similarly, the remaining light modulatingelement columns form corresponding modulating element groups thatimplement the remaining pixel image data portions of line image dataportions LIN11 (e.g., column C4 forms group G4 that implements pixelimage data portion PID14, and column C8 forms group G8 that implementspixel image data portion PID18. Note that modulating element groupsG1-G8 are written into spatial light modulator 120H in an “upside-downand backward” manner such that pixel image data bit PID111 of pixelimage data portion PID11 is written an inverted (upside-down) mannerinto a lowermost modulating element of modulating element group G1(i.e., the lower left portion of array 122H when viewed from the front),and pixel image data bit PID188 of pixel image data portion PID18 iswritten in an inverted (upside-down) manner in the upper portion ofmodulating element group G8 (i.e., the upper right portion of array 122Hwhen viewed from the front). As indicated by the double-dot-dash linesin FIG. 8, cross-process optical subsystem 133H utilizes one or morecylindrical/acylindrical lenses to invert modulated light field 119Asuch that the light modulating elements configured by pixel image dataPID11 generate pixel image P11 on the right side of elongated imagingregion 167H, and the light modulating elements configured by pixel imagedata PID18 generate pixel image P18 on the upper left side of elongatedimaging region 167H. In addition, process optical subsystem 137Hutilizes one or more cylindrical/acylindrical mirrors to invert theimaged light field received from cross-process optical subsystem 133Hsuch that (non-inverted) pixel image portion (which is generated by themodulating element implementing pixel image data bit PID111) appears inthe upper-left portion of elongated imaging region 167H, and such that(non-inverted) pixel image P188 (which is generated by the modulatingelement implementing pixel image data bit PID188) appears in thelower-right portion of elongated imaging region 167H.

Multi-level image exposure is achieved using imaging system 100H byconfiguring groups of MEMS mirror mechanisms of DMD-type spatial lightmodulator 120H that are substantially aligned in the process (Y-axis)direction such that “partially on” pixel images are implemented byactivating contiguous MEMS mirror mechanisms that are disposed in thecentral region of the associated MEMS mirror mechanism group. Forexample, in the exemplary embodiment shown in FIG. 8, modulating elementgroup G1 consists of the modulating elements 125H disposed in column C1,where group G1 is configured in accordance with a first image pixel dataportion PID11 such that all of the modulating elements are disposed an“on” modulated state (indicated by the white filling each element),whereby a pixel image P11 is generated on imaging surface 162H having amaximum brightness. Similarly, modulating element group G8 consists ofthe modulating elements 125H disposed in column C8, where group G8 isconfigured in accordance with an image pixel data portion PID18 suchthat all of the modulating elements are disposed an “off” modulatedstate (indicated by the slanted-line filling each element), whereby adark pixel image P18 is generated on imaging surface 162H. The remaininggroups (columns) of MEMS mirror mechanisms are configured using threeexemplary “partially on” gray-scale values. For example, group G2 isconfigured by pixel image data portion PID12 having a “mostly on”gray-scale value such that two deactivated MEMS mirror mechanismsdisposed at the top and bottom of column C2, and six activated MEMSmirror mechanisms disposed between the deactivated MEMS mirrormechanisms. In contrasts, group G7 is configured by a pixel image dataportion having a “barely on” gray-scale value including six deactivatedMEMS mirror mechanisms disposed at the top and bottom of column C7 andtwo activated MEMS mirror mechanisms disposed between the deactivatedMEMS mirror mechanisms, and group G5 is configured by a pixel image dataportion having a “medium on” gray-scale value including four deactivatedMEMS mirror mechanisms disposed at the top and bottom of column C5 andfour activated MEMS mirror mechanisms disposed between the deactivatedMEMS mirror mechanisms.

FIGS. 9, 10(A), 10(B) and 10(C) are simplified side views showing aportion of imaging system 100H (see FIG. 8) during an exemplary imagingoperation. Note that the simplified side views ignore inversion in thecross-process direction and the downward reflection of imaged andconcentrated light, and as such catadioptric anamorphic optical system130H is depicted by a rectangular box.

FIG. 9 illustrates imaging system 100H(T1) (i.e., imaging system 100Hduring a first time period T1 of the imaging operation) when exemplarymodulating element group G2 of spatial light modulator 120H isrespectively configured in accordance with line image data group PID12in the manner described above with reference to FIG. 8. In particular,FIG. 9 depicts the configuration of modulating elements 125H-21 to125H-28 using pixel image data portion PID12 such that MEMS mirrormechanisms 125H-22 to 125H-27 are activated and MEMS mirror mechanisms125H-21 and 125H-28 are deactivated.

Referring to the right side of FIG. 9, to implement an image transferoperation, imaging system 100H further includes a liquid source 190 thatapplies a fountain solution 192 onto imaging surface 162H at a pointupstream of the imaging region, an ink source 195 that applies an inkmaterial 197 at a point downstream of imaging region. In addition, atransfer mechanism (not shown) is provided for transferring the inkmaterial 197 to a target print medium, and a cleaning mechanism 198 isprovided for preparing imaging surface 162H for the next exposure cycle.The image transfer operation is further described below with referenceto FIGS. 10(A) to 10(C).

Referring again to FIG. 9, because of their activated configurationstate, MEMs mirror mechanisms (light modulating elements) 125H-22 to125H-27 reflect portions of homogenous light field 119A such thatmodulated light portions 118B-21 to 118B-27 are directed throughcatadioptric anamorphic optical system 130H (note that homogeneous lightportions are redirected away from catadioptric anamorphic optical system130H by deactivated MEMs mirror mechanisms 125H-21 and 125H-28).Modulated light portions 118B-21 to 118B-27 form modulated light field119B that is imaged and concentrated by catadioptric anamorphic opticalsystem 130H, thereby generating concentrated modulated light field 119Cthat produces pixel image P12, which forms part of a line image SL1 inan elongated imaging region 167H-1 on imaging surface 162H. Inparticular, the concentrated light associated formed by modulated lightportions 118B-21 to 118B-27 removes (evaporates) fountain solution 192from the elongated imaging region 167H-1 (i.e., such that a portion ofimaging surface 162H at pixel image P21 is exposed). Note that the sizeof pixel image P21 (i.e., the amount of fountain solution that isremoved from imaging surface 162H) is determined by number of activatedMEMs mirror mechanisms.

FIGS. 10(A), 10(B) and 10(C) show imaging system 100H at timessubsequent to time T1, where spatial light modulator 120H is deactivatedin order to how surface feature P12 (see FIG. 9) is subsequentlyutilized in accordance with the image transfer operation of imagingsystem 100H. Referring to FIG. 10(A), at a time T2 drum cylinder 160Hhas rotated such that surface region 162H-1 has passed under ink source195. Due to the removal of fountain solution depicted in FIG. 9, inkmaterial 197 adheres to exposed surface region 162H-1 to form an inkfeature TF. Referring to FIG. 10(B), at a time T3 while ink feature TFis passing the transfer point, the weak adhesion between the inkmaterial and surface region 162H-1 and the strong attraction of the inkmaterial to the print medium (not shown) causes ink feature TF totransfer to the print medium, resulting in a “dot” in the ink printed onthe print medium. At a subsequent T4, as indicated in FIG. 10(C),surface region 162H-1 is rotated under cleaning mechanism 198, whichremoves any residual ink and fountain solution material to preparesurface region 162H-1 for a subsequent exposure/print cycle. Accordingto the above-described image transfer operation, ink material onlytransfers onto portions of imaging surface 162H that are exposed by theimaging process described above (i.e., ink material does not adhere tofountain solution 192), whereby ink material is only transferred to theprint medium from portions of drum roller 160H that are subjected toconcentrated light as described herein. Thus, variable data fromfountain solution removal is transferred, instead of constant data froma plate as in conventional systems. For this process to work using arastered light source (i.e., a light source that is rastered back andforth across the scan line), a single very high power light (e.g.,laser) source would be required to sufficiently remove the fountainsolution in real time. A benefit of the imaging operation of the presentinvention is that, because liquid is removed from the entire scan linesimultaneously, an offset press configuration is provided at high speedusing multiple relatively low power light sources.

The present invention will now be described with reference to twoexemplary specific embodiments. Those skilled in the art will recognizethat these exemplary embodiments may be modified to include additionaloptical elements without changing the spirit and scope of the presentinvention, and therefore the exemplary embodiments are not intended tobe limiting unless otherwise specified in the claims.

FIGS. 11 and 12 are simplified top and side view diagrams showing animaging system 100J including a catadioptric anamorphic optical system130J arranged in accordance with a first specific embodiment of thepresent invention. Catadioptric anamorphic optical system 130J isdisposed between a simplified spatial light modulator 120J and asimplified imaging surface 162J for brevity, and it is understood thatthese components may be implemented using the alternative structures anddetails described above.

Referring to FIGS. 11 and 12, catadioptric anamorphic optical system130J includes a field lens 132J, a cross-process optical subsystem 133Jand a process optical subsystem 137J. Cross-process optical subsystem133J includes doublet (first and second) cylindrical/acylindrical lenselements 134J and 135J that are cooperatively shaped and arranged toimage modulated light field 119B onto imaging surface 162J in thecross-process direction in a manner consistent with the ray trace(dashed) lines shown in FIG. 11. That is, doublet lens elements 134J and135J have optical surfaces that have a constant curved profile centeredalong the neutral or zero-power axis that is parallel to the process(X-axis) direction, and these lenses are positioned between spatiallight modulator 120J and imaging surface 162J such that line image SLhas a predetermined length in the process direction on imaging surface162J. Optional collimating field lens 132J is a cross-process directioncylindrical/acylindrical lens that is positioned between spatial lightmodulator 120J and lens element 134J, and is cooperatively formed withlens element 134J to converge light in the cross-process (X-axis)direction at a point between doublet lens elements 134J and 135J,thereby enabling the positioning of an aperture stop between doubletlens elements 134J and 135J. This arrangement enables efficientcorrection of aberrations using a low number of simple lenses, and alsoand minimizes the size of doublet lens elements 134J and 135J. Fieldlens 132J also serves to collimate the light portions that are slightlydiverging off of the surface of the spatial light modulator 120J.Process optical subsystem 137J includes a singlecylindrical/acylindrical mirror element 138J that is shaped andpositioned to image and concentrate light received from cross-processoptical subsystem 133J in the process (Y-axis) direction onto imagingsurface 162J in a manner consistent with the ray trace lines shown inFIG. 12. As the focusing power of lens 138J is increased, the intensityof the light on spatial light modulator 120J is reduced relative to theintensity of the line image SL. However, this means thatcylindrical/acylindrical mirror 138J must be placed closer to theimaging surface 162J.

FIGS. 13 and 14 are simplified top and side view diagrams showing animaging system 100J including a catadioptric anamorphic optical system130J arranged in accordance with a second specific embodiment of thepresent invention. Catadioptric anamorphic optical system 130K isdepicted between a spatial light modulator 120K and an imaging surface162K, but may be used in other arrangements as mentioned above.Catadioptric anamorphic optical system 130K includes a field lens 132K,a cross-process optical subsystem 133K and a process optical subsystem137K arranged in order. Cross-process optical subsystem 133K includestriplet cylindrical/acylindrical lens elements 134K, 135K and 136K thatare cooperatively shaped and arranged to image modulated light field119B onto imaging surface 162K in the cross-process direction in themanner indicated by the ray trace lines in FIG. 13. Field lens 132K is across-process direction cylindrical/acylindrical lens that is positionedbetween spatial light modulator 120K and lens element 134K, and iscooperatively shaped and positioned with lens elements 134K and 135K toenable locating the aperture Y-stop between (second and third) lenselements 135K and 136K of cross-process optical subsystem 133K,providing benefits similar to those described above with reference tofield lens 132J. Process optical subsystem 137K includes a singlecylindrical/acylindrical mirror element 138K that is shaped and arrangedto image and concentrate modulated light field 119B in the process(Y-axis) direction onto imaging surface 162K in a manner consistent withthe ray trace lines shown in FIG. 14.

FIG. 15 is a perspective view showing an imaging system 100P utilizing ahomogenous light generator 110P, a DMD-type spatial light modulator120P, and a multiple-mirror-type catadioptric anamorphic optical system130K according to another specific embodiment of the present invention.Spatial light modulator 120P is essentially identical to DMD-typespatial light modulator 120G (described above), and is positioned at acompound angle relative to homogenous light generator 110P in order togenerate modulated light field 119B in response to image datatransmitted from a controller 180P in the manner similar to thatdescribed above. DMD-type imaging system 100P differs from the previousembodiments in that it includes a process optical subsystem 137Putilizing at least two mirrors to generate a line image SL1 on imagingsurface 162P of a drum roller 160P. Specifically, similar to the opticalsystems described above, catadiotropic anamorphic optical system 130Pincludes a cross-process optical subsystem 133P formed by one or morecylindrical/acylindrical lenses, but has a process optical subsystem137Q formed by at least two mirrors, at least one of which being acylindrical/acylindrical mirror. The multi-mirror-type catadioptricanamorphic optical system architecture, which is illustrated in FIG. 15and described in additional detail below with reference to FIGS. 16-19,provides the lower level of distortion in the process direction andlower sagittal field curvature across the cross-process direction thatis characteristic of catadioptric anamorphic optical systems, and alsoallows positioning of the imaging surface (e.g., a drum cylinder) on aside of the optical system (i.e., instead of below the optical system aspresented in the embodiments described above).

FIGS. 16 and 17 are simplified top and side view diagrams showing animaging system 100Q including a first multi-mirror-type catadiotropicanamorphic optical system 130Q arranged in accordance with anotherspecific embodiment of the present invention. Optical system 130Q isdepicted as forming a light path between a spatial light modulator 120Qand an imaging surface 162Q, but may be used in other apparatus ordevices as mentioned above. Anamorphic optical system 130Q includes afield lens 132Q, a cross-process optical subsystem 133Q and a processoptical subsystem 137Q. Cross-process optical subsystem 133Q includestriplet cylindrical/acylindrical lens elements 134Q, 135Q and 136Q thatare cooperatively shaped and arranged to image modulated light field119B onto imaging surface 162Q in the cross-process direction in themanner indicated by the ray trace lines in FIG. 16. Field lens 132Q is across-process direction cylindrical/acylindrical lens that is positionedbetween spatial light modulator 120Q and lens element 134Q, and iscooperatively shaped and positioned with lens elements 134Q and 135Q toenable locating the aperture stop between (second and third) lenselements 135Q and 136Q, thereby providing benefits similar to thosedescribed above with reference to field lens 132J. Process opticalsubsystem 137Q includes a separated fold (flat) mirror 138Q and acylindrical/acylindrical mirror 139Q that is shaped and arranged toimage and concentrate modulated light field 119B in the process (Y-axis)direction onto imaging surface 162Q in a manner consistent with the raytrace lines shown in FIG. 17.

Table 1 includes an optical prescription for the opposing surfaces ofeach optical element of optical system 130Q. In Table 1 (and Table 2,provided below), the surface of each element facing the optical systeminput (light source) is referred to as “S1”, and the surface of eachelement facing the optical system output is referred to as “S2”. Forexample, “132Q: S1” refers to the surface of field lens 132Q that facesspatial light modulator 120Q. Curvature values are in 1/millimeter andthickness values are in millimeters. Note that both the light source(i.e., the surface of spatial light modulator 120Q) and the targetsurface (i.e., imaging surface 162Q) are assumed planar for purposes ofthe listed prescription. The optical prescription also assumes a lightwavelength of 980 nm. The resulting optical system has a cross-processdirection magnification of 0.33.

TABLE 1 THICK- GLASS SURFACE SHAPE Y-CURVE Y-RADIUS X-CURVE X-RADIUSNESS TYPE 132Q: S1 PLANO 0.00000000 INFINITY 0.00000000 INFINITY 10.000BK7 132Q: S2 CONVEX 0.01903430 52.537 0.00000000 INFINITY 73.983 134Q:S1 CONVEX 0.01044659 95.725 0.00000000 INFINITY 12.500 SF10 134Q: S2PLANO 0.00000000 INFINITY 0.00000000 INFINITY 12.912 135Q: S1 CONVEX0.03279483 30.493 0.00000000 INFINITY 5.000 SF10 135Q: S2 CONCAVE0.03729411 26.814 0.00000000 INFINITY 45.000 STOP PLANO 0.00000000INFINITY 0.00000000 INFINITY 120.726 136Q: S1 PLANO 0.00000000 INFINITY0.00000000 INFINITY 12.500 SF10 136Q: S2 CONVEX 0.00564295 177.212 0.00000000 INFINITY 146.217 138Q PLANO 0.00000000 INFINITY 0.00000000INFINITY −125.00 MIRROR 139Q CONCAVE 0.00000000 INFINITY 0.00349853285.834 189.156 MIRROR

FIGS. 18 and 19 are simplified top and side view diagrams showing animaging system 100R including a second multi-mirror-type catadiotropicanamorphic optical system 130R arranged in accordance with anotherspecific embodiment of the present invention. Optical system 130R formsa light path between a spatial light modulator 120R and an imagingsurface 162R, but may be used in other arrangements as mentioned above.Anamorphic optical system 130R includes a field lens 132R, across-process optical subsystem 133R and a process optical subsystem137R. Cross-process optical subsystem 133R includes tripletcylindrical/acylindrical lens elements 134R, 135R and 136R that arecooperatively shaped and arranged to image modulated light field 119Bonto imaging surface 162R in the cross-process direction in the mannerindicated by the ray trace lines in FIG. 18. Field lens 132R is across-process direction cylindrical/acylindrical lens that is positionedbetween spatial light modulator 120R and lens element 134R, and iscooperatively shaped and positioned with lens elements 134R and 135R toenable locating the aperture stop between (second and third) lenselements 135R and 136R, thereby providing benefits similar to thosedescribed above with reference to field lens 132J. Process opticalsubsystem 137R includes (first and second) cylindrical/acylindricalmirrors 138Q and 139Q that are cooperatively shaped and arranged toimage and concentrate modulated light field 119B in the process (Y-axis)direction onto imaging surface 162R in a manner consistent with the raytrace lines shown in FIG. 19. Table 2 includes an optical prescriptionfor the opposing surfaces of each optical element of catadiotropicanamorphic optical system 130R. The optical prescription assumes a lightwavelength of 980 nm, and the resulting optical system has across-process direction magnification of 0.44.

TABLE 2 THICK- GLASS SURFACE SHAPE Y-CURVE Y-RADIUS X-CURVE X-RADIUSNESS TYPE 132R: S1 PLANO 0.00000000 INFINITY 0.00000000 INFINITY 10.000BK7 132R: S2 CONVEX 0.02239886 44.645 0.00000000 INFINITY 75.729 134R:S1 CONVEX 0.01076421 92.900 0.00000000 INFINITY 12.274 SF10 134R: S2PLANO 0.00000000 INFINITY 0.00000000 INFINITY 13.248 135R: S1 CONVEX0.03329329 30.036 0.00000000 INFINITY 5.000 SF10 135R: S2 CONCAVE0.03802478 26.299 0.00000000 INFINITY 22.000 STOP PLANO 0.00000000INFINITY 0.00000000 INFINITY 155.962 136R: S1 PLANO 0.00000000 INFINITY0.00000000 INFINITY 12.274 SF10 136R: S2 CONVEX 0.00552966 180.843 0.00000000 INFINITY 123.866 138R CONCAVE 0.00000000 INFINITY 0.0019701911.567 99.568 MIRROR 139R CONCAVE 0.00000000 INFINITY 0.00260405384.018 193.169 MIRROR

Although the present invention has been described with respect tocertain specific embodiments, it will be clear to those skilled in theart that the inventive features of the present invention are applicableto other embodiments as well, all of which are intended to fall withinthe scope of the present invention. For example, although the presentinvention is illustrated as having light paths that are linear (see FIG.1), having one fold (see FIG. 8), or having two folds (see FIG. 15),other arrangements may be contemplated by those skilled in the art thatinclude folding along any number of arbitrary light paths. In addition,the methods described above for generating a high energy line image maybe achieved using devices other than those described herein.

1. A single-pass imaging system for generating a substantiallyone-dimensional line image that extends in a cross-process direction onan imaging surface in accordance with an image data file, the systemcomprising: means for generating a two-dimensional modulated light fieldincluding light portions having a first light intensity; and acatadioptric anamorphic optical system including: at least onecylindrical/acylindrical lens element operably positioned and arrangedto image the two-dimensional modulated light field in the cross-processdirection, and at least one cylindrical/acylindrical mirror elementoperably positioned and arranged to image and concentrate the imagedmodulated light field in the process direction such that said imaged andconcentrated modulated light field forms said substantiallyone-dimensional line image on said imaging surface.
 2. The imagingsystem according to claim 1, wherein the catadioptric anamorphic opticalsystem further comprises: a cross-process optical subsystem includingsaid at least one cylindrical/acylindrical lens element; and aprocess-direction optical subsystem including said at least one at leastone cylindrical/acylindrical mirror element, wherein the cross-processoptical subsystem is positioned and arranged to receive thetwo-dimensional modulated light field from said means, and to transmitimaged light to the process-direction optical subsystem, and wherein theprocess-direction optical subsystem is positioned and arranged toreceive the imaged light from the cross-process optical subsystem, andto transmit imaged and concentrated light onto the imaging surface. 3.The imaging system according to claim 2, wherein the catadioptricanamorphic optical system further comprises a collimatingcylindrical/acylindrical field lens positioned between saidcross-process optical subsystem and said modulated light fieldgenerating means, said collimating cylindrical/acylindrical field lensbeing arranged to collimate divergent light received from said modulatedlight field generating means.
 4. The imaging system according to claim3, wherein the cross-process optical subsystem comprises a firstcylindrical/acylindrical lens and a second cylindrical/acylindrical lensthat are cooperatively shaped and positioned to image thetwo-dimensional modulated light field in the cross-process direction onthe imaging surface.
 5. The imaging system according to claim 4, whereinthe catadioptric anamorphic optical system further comprises an aperturestop disposed between first cylindrical/acylindrical lens and the secondcylindrical/acylindrical lens.
 6. The optical system according to claim3, wherein the cross-process optical subsystem comprises a firstcylindrical/acylindrical lens, a second cylindrical/acylindrical lensand a third cylindrical/acylindrical lens that are cooperatively shapedand positioned to image the two-dimensional modulated light field in thecross-process direction on the imaging surface.
 7. The imaging systemaccording to claim 6, wherein the catadioptric anamorphic optical systemfurther comprises an aperture stop disposed between secondcylindrical/acylindrical lens and the third cylindrical/acylindricallens.
 8. The imaging system according to claim 6, wherein theprocess-direction optical subsystem comprises two or more mirrors. 9.The imaging system according to claim 6, wherein the process-directionoptical subsystem comprises a flat fold mirror that is positioned toreflect the imaged light onto the at least one cylindrical/acylindricalmirror.
 10. The imaging system according to claim 9, wherein saidmodulated light field generating means comprises: a homogenous lightgenerator including at least one light source for generating one or morelight beams, and at least one light homogenizer including means forhomogenizing said one or more light beams such that portions of saidhomogenized light beams form a homogeneous light field, and a spatiallight modulator including a plurality of light modulating elementsdisposed in an array, and means for individually configuring theplurality of light modulating elements into one of a first modulatedstate and a second modulated state in accordance with the image datafile such that the two-dimensional light field is generated only byportions of the homogeneous light field directed from first lightmodulating elements of said array in the first modulated state.
 11. Theimaging system according to claim 10, wherein the plurality of lightmodulating elements are arranged in a plurality of rows and a pluralityof columns, wherein each said column includes an associated group ofsaid plurality of light modulating elements, and wherein the anamorphicoptical system is arranged to concentrate modulated light portionsreceived from each associated group of said plurality of lightmodulating elements of each said column onto an associated line imageportion of said elongated line image.
 12. The imaging system accordingto claim 11, wherein each of the plurality of light modulating elementscomprises a microelectromechanical (MEMs) mirror mechanism disposed on asubstrate, wherein each MEMs mirror mechanism includes a mirror andmeans for supporting and moving the mirror between a first tiltedposition relative to the substrate, and a second tilted positionrelative to the substrate, according to said associated control signalsgenerated by the controller, and wherein the homogenous light generator,the spatial light modulator and the anamorphic optical system arepositioned such that, when the mirror of each said MEMs mirror mechanismis in the first tilted position, said mirror reflects an associatedreceived homogenous light portion such that said modulated light portionis directed to the anamorphic optical system, and when said mirror ofeach said MEMs mirror mechanism is in the second tilted position, saidmirror reflects said associated received homogenous light portion suchthat said reflected received homogenous light portion is directed awayfrom the anamorphic optical system.
 13. The imaging system according toclaim 6, wherein the process-direction optical subsystem comprises afirst cylindrical/acylindrical mirror and a secondcylindrical/acylindrical mirror that are respectively shaped andpositioned to cooperatively concentrate the image light in the processdirection onto the imaging surface.
 14. The imaging system according toclaim 13, wherein said modulated light field generating means comprises:a homogenous light generator including at least one light source forgenerating one or more light beams, and at least one light homogenizerincluding means for homogenizing said one or more light beams such thatportions of said homogenized light beams form a homogeneous light field,and a spatial light modulator including a plurality of light modulatingelements disposed in an array, and means for individually configuringthe plurality of light modulating elements into one of a first modulatedstate and a second modulated state in accordance with the image datafile such that the two-dimensional light field is generated only byportions of the homogeneous light field directed from first lightmodulating elements of said array in the first modulated state.
 15. Theimaging system according to claim 14, wherein the plurality of lightmodulating elements are arranged in a plurality of rows and a pluralityof columns, wherein each said column includes an associated group ofsaid plurality of light modulating elements, and wherein the anamorphicoptical system is arranged to concentrate modulated light portionsreceived from each associated group of said plurality of lightmodulating elements of each said column onto an associated line imageportion of said elongated line image.
 16. The imaging system accordingto claim 15, wherein each of the plurality of light modulating elementscomprises a microelectromechanical (MEMs) mirror mechanism disposed on asubstrate, wherein each MEMs mirror mechanism includes a mirror andmeans for supporting and moving the mirror between a first tiltedposition relative to the substrate, and a second tilted positionrelative to the substrate, according to said associated control signalsgenerated by the controller, and wherein the homogenous light generator,the spatial light modulator and the anamorphic optical system arepositioned such that, when the mirror of each said MEMs mirror mechanismis in the first tilted position, said mirror reflects an associatedreceived homogenous light portion such that said modulated light portionis directed to the anamorphic optical system, and when said mirror ofeach said MEMs mirror mechanism is in the second tilted position, saidmirror reflects said associated received homogenous light portion suchthat said reflected received homogenous light portion is directed awayfrom the anamorphic optical system.
 17. A single-pass imaging system forgenerating a substantially one-dimensional line image that extends in across-process direction on an imaging surface in accordance with animage data file, the system comprising: a homogenous light generatorincluding at least one light source for generating one or more lightbeams, and at least one light homogenizer including means forhomogenizing said one or more light beams such that portions of saidhomogenized light beams form a homogeneous light field, and a spatiallight modulator including a plurality of light modulating elementsdisposed in an array, and means for individually configuring theplurality of light modulating elements into one of a first modulatedstate and a second modulated state in accordance with the image datafile such that the two-dimensional light field is generated only byportions of the homogeneous light field directed from first lightmodulating elements of said array in the first modulated state; and acatadioptric anamorphic optical system including: at least onecylindrical/acylindrical lens element operably positioned and arrangedto image the two-dimensional modulated light field in the cross-processdirection, and at least two mirror elements including at least onecylindrical/acylindrical mirror element, said at least two mirrorelements respectively operably positioned and arranged to cooperativelyimage and concentrate in the process direction imaged light receivedfrom the at least one cylindrical/acylindrical lens element such thatimaged and concentrated modulated light field transmitted from said atleast two mirror elements forms said substantially one-dimensional lineimage on said imaging surface.
 18. The imaging system according to claim17, wherein the process-direction optical subsystem comprises a flatfold mirror element is positioned to reflect the imaged light receivedfrom the at least one cylindrical/acylindrical lens element onto the atleast one cylindrical/acylindrical mirror element.
 19. The imagingsystem according to claim 17, wherein the process-direction opticalsubsystem comprises a first cylindrical/acylindrical mirror and a secondcylindrical/acylindrical mirror that are respectively shaped andpositioned to cooperatively concentrate the image light in the processdirection onto the imaging surface.
 20. A single-pass imaging system forgenerating a substantially one-dimensional line image that extends in across-process direction on an imaging surface in accordance with animage data file, the system comprising: a homogenous light generatorincluding at least one light source for generating one or more lightbeams, and at least one light homogenizer including means forhomogenizing said one or more light beams such that portions of saidhomogenized light beams form a homogeneous light field; a spatial lightmodulator including a plurality of light modulating elements disposed inan array, and means for individually configuring the plurality of lightmodulating elements into one of a first modulated state and a secondmodulated state in accordance with the image data file such that thetwo-dimensional modulated light field is generated only by portions ofthe homogeneous light field directed from first light modulatingelements of said array in the first modulated state, wherein thetwo-dimensional modulated light field has a first width in thecross-process direction and a first height in the process direction; anda catadioptric anamorphic optical system for imaging and concentratingthe two-dimensional light field to generate said substantiallyone-dimensional line image on the imaging surface, the catadioptricanamorphic optical system including: at least onecylindrical/acylindrical lens element operably positioned and arrangedto image and expand the two-dimensional modulated light field in thecross-process direction such said substantially one-dimensional lineimage has a second width in the cross-process that is equal to orgreater than the first width of the two-dimensional modulated lightfield; and at least two cylindrical/acylindrical mirror element operablypositioned and arranged to image and concentrate the imaged and expandedmodulated light field in the process direction such that saidsubstantially one-dimensional line image has a second width in theprocess direction that is at least three times smaller than the firstheight of the two-dimensional modulated light field.